1. Field of the Invention
The present invention relates to a liquid injection system for injecting liquid into a patient by relatively moving a cylinder and a piston of a liquid syringe that is mounted on a liquid injector, and more particularly relates to a liquid injection system in which a liquid syringe is mounted on a liquid injector by a cylinder adapter.
2. Description of the Related Art
Presently available imaging diagnostic apparatus for capturing fluoroscopic images of patients include CT (Computed Tomography) scanners, MRI (Magnetic Resonance Imaging) apparatus, PET (Positron Emission Tomography) apparatus, ultrasonic diagnostic apparatus, angiography apparatus, and MRA (MR Angiography) apparatus.
When such imaging diagnostic apparatus are used to capture a fluoroscopic image of a patient, it is occasionally practiced to inject a liquid such as a contrast medium or a saline solution into the patient. This liquid injector for automatically injecting a liquid into a patient has practical application. Such a liquid injector has a main injector body on which a liquid syringe is removably mounted.
The liquid syringe has a hollow cylinder filled with a liquid and a cylindrical piston slidably inserted in the cylinder. Generally, the cylinder has an annular cylinder flange disposed on the outer circumferential edge of the rear end thereof, and the piston has an annular piston flange disposed on the outer circumferential edge of the rear end thereof.
When the liquid injector is in use, the cylinder of the liquid syringe which is filled with the liquid is connected to the patient by an extension tube, and the liquid syringe is mounted on the main injector body. In general liquid injectors, the main injector body has a recess defined in its upper surface complementary in shape to the cylinder of the liquid syringe and its cylinder flange. Therefore, the liquid syringe is held on the main injector body when the cylinder and the cylinder flange are placed in the recess.
The liquid injector also has a syringe actuating mechanism for holding the piston flange independently of the cylinder and sliding the piston into and out of the cylinder. When the piston is pushed into the cylinder, the liquid in the cylinder can be injected into the patient. When the piston is pulled out of the cylinder, the cylinder can draw the liquid from a liquid container.
Generally, in order to allow the liquid injector to hold a various types of liquid syringes having various shapes, the recess defined in the upper surface of the main injector body is shaped to be able to receive the cylinder of the liquid syringe having the maximum size. Liquid syringes having sizes other than the maximum size are combined with respective dedicated cylinder adapters and placed in the recess in the main injector body.
Cylinder adapters generally have recesses defined in their upper surfaces complementary in shape to the cylinders of the liquid syringes and their cylinder flanges. The cylinders of the liquid syringes and their cylinder flanges are held in the recesses in the cylinder adapters. The cylinder adapters have lower surfaces whose outer profiles are similar to the outer profile of the cylinder of the liquid syringe having the maximum size and the cylinder flange thereof, and are placed in the recess in the main injector body.
Liquid injectors constructed as described above have been invented by the inventor of the present invention and filed for patent (see, for example, Patent documents 1 and 2 shown below):
Patent document 1: Japanese laid-open patent publication No. 2002-11096.
Patent document 2: Japanese laid-open patent publication No. 2002-102343.
The above liquid injectors hold a liquid syringe when the cylinder is directly placed in the recess in the main injector body or when the cylinder adapter with the cylinder mounted in its recess is placed in the recess in the main injector body.
However, since the liquid syringe or the cylinder adapter is merely placed in the recess in the main injector body, it is difficult to keep the liquid syringe or the cylinder adapter securely retained in the recess. As a result, the liquid syringe or the cylinder adapter may possibly be incompletely be retained in the recess, and hence may possibly be dislodged from the recess while the liquid is being injected from the liquid syringe into the patient.
One liquid injector that has been proposed to solve the above problems has a clamp mechanism disposed in the recess in the main injector body for clamping the cylinder flange of a liquid syringe or the adapter flange of a cylinder adapter.
However, even the proposed liquid injector fails to reliably hold liquid syringes because the cylinder adapters simply hold corresponding liquid syringes by placing them in recesses defined in the cylinder adapters.